Compositions designed for use in automatic dishwasher machines are well known, and a consistent effort has been made by detergent manufacturers to improve the cleaning and/or rinsing efficiency of said compositions on chinaware, glassware and silverware, as reflected by numerous patent publications.
Particulate detergent compositions are, in general, designed to be white in colour. It has however, been seen to be desirable to include in such compositions, at low levels, particles coloured with various dyestuffs, which are commonly known as `speckle` particles.
Most commonly, speckle particles are based on enzyme-containing prills to which coloured dyestuffs have been applied. This has the disadvantage to the formulator of a detergent product that the amount of speckle, and hence colour in the product is related to the in-product level of the enzyme component whose stain removal performance is highly sensitive to its level of inclusion. Varying the level of the enzyme to achieve the desirable level of speckle effect in product can thus have a major impact on the peformance of the detergent product.
In choosing an alternative speckle base/substrate the formulator faces a problem that such substrate should have no negative effect on the detergent performance of the product, and preferably should contribute to the detergency performance.
The fomulator is also faced with the problem that the speckle should have good abrasion colour stability, that is good resistance to dye abrasion (e.g. in any further packaging/processing steps). Similarly, the colour of the speckle should be resistant to being washed off in any further processing steps involving liquid application, e.g. by spraying-on, steps. The speckle furthermore should possess good in-product colour storage stability including resistance to oxidation and other processes which may cause degradation of the dyestuff.
The Applicants have now found that particles of hygroscopic material, particularly silicate material, are especially suitable speckle substrates. It has also been found that improved abrasion colour stability, stability to liquid spray contact and in-product storage stability may be achieved when the speckle is made by a process whereby an aqueous mixture of an organic binder and the dyestuff ar e sprayed onto base particles of hygroscopic material, and subsequently dried.
Surprisingly, the Applicants have also found that when such a silicate-containing speckle material is incorporated as part of a silicate-based alkalinity system, in place of a significant proportion of the usual (non-speckle) silicate, prevention of filming and clouding benefits on glassware are obtained. Such benefits are furthermore obtainable even in the absence of the dyestuff (i.e. with just the organic binder applied to the base hygroscopic particle).